Today, various methods for hemodialysis are known, which include so-called double-needle or dual-needle (DN) dialysis and single-needle (SN) dialysis.
In DN dialysis, blood is withdrawn from a patient via one access device (e.g. a needle or catheter), and returned to the patient via another access device (e.g. a needle or catheter). A DN dialysis system is typically configured to generate a steady flow of blood from and to the patient, and to pump the blood continuously through the dialyzer.
In SN dialysis, one and the same access device (e.g. needle or catheter) is used for withdrawing and returning blood, which may be advantageous in a self-care setting since there is little risk of significant blood loss if the access device is accidentally dislodged from the patient. Also, when using SN dialysis, fewer needle punctures for accessing the patient's blood are required compared to DN dialysis. However, since SN dialysis withdraws and returns blood cyclically via one and the same access device, more time may be required for completing a dialysis treatment in comparison with DN dialysis.
Accordingly, DN dialysis has both advantages and disadvantages in comparison with SN dialysis, and vice versa. For this reason, it is desirable to offer blood treatment devices and dialysis machines that allow both DN and SN operation.
For home dialysis, as well as for dialysis in a clinical setting, it may be desirable to provide part of the dialysis system as a disposable which is designed to be attached to a dialysis machine. For ease of use and patient safety, such a disposable may comprise the extracorporeal blood circuit, including blood lines, connectors for access device(s), a dialyzer and a blood pump. At the start of a treatment, in such a scenario, the disposable may be connected to a dialysis machine so as to receive appropriately conditioned dialysis fluid and to be controlled to circulate the dialysis fluid through the dialyzer. After completed treatment, the disposable may be disconnected from the dialysis machine and discarded.
U.S. Pat. No. 6,645,166 discloses a disposable kit that permits both SN and DN operation when connected to a dialysis machine. The disposable kit comprises a dialyzer with an inlet connected to a feed line and an outlet connected to a return line. The feed line comprises two parallel line branches, each having a membrane pump. Each membrane pump comprises a pressure chamber, which is controlled to expand or compress by being alternately filled and emptied of a gas or a liquid, and electromagnetically or pneumatically actuated control valves on both sides of the pressure chamber to control the direction of the blood flow generated by the pressure chamber. For DN operation, the feed and return lines are connected to different access devices, and for SN operation, the feed and return lines are connected to a common access device. A connection line is arranged to extend between the outlet of the dialyzer and one of the membrane pumps and is provided with a control valve which is controlled to open or close to ensure a continuous flow of blood through the dialyzer in both DN and SN operation. Such a disposable kit requires use of a special dialysis machine, which has a dedicated system for alternately filling and emptying the pressure chamber with gas/liquid. It also requires the dialysis machine to provide proper control signals for the control valves. Still further, the disposable defines relatively complicated blood flow paths, which may lead to in an elevated risk for clogging, blood leakage and/or hemolysis.
The prior art also comprises US2009/0137940, which discloses a double diaphragm pump for application as a single use disposable medical blood pump, e.g. in dialysis systems. The pump comprises two pump chambers connected in parallel, where each pump chamber contains a flexible chamber diaphragm for pumping blood. An inlet valve and an outlet valve, in the form of diaphragm valves, are arranged on either side of each pump chamber. The operation of the pump is controlled by selectively applying vacuum or pneumatic pressure to the chamber diaphragm and the diaphragm valves. The pump is suggested for use in a dual-needle hemodialysis system, e.g. to generate a substantially constant blood flow from the patient to the extracorporeal circuit and/or from extracorporeal circuit to the patient, or to provide a pulsatile blood flow to the dialyzer downstream of the pump in the extracorporeal circuit and essentially constant blood flow from the patient to the extracorporeal circuit.
A similar pump, denoted PULSAR™ Blood Movement System, is described in “Renal Solutions™—Blood Pump”, located at http://www.t-med.co.uk/dialysis/renalsolutions-bloodpump.htm. This pump consists of two chambers with a flexible medial diaphragm in each chamber. The top and bottom of each chamber opens to bloodlines; the back is attached to a pneumatic system, which is used to move the diaphragm. During dialysis, clamps below the chambers open and a vacuum is used to draw the diaphragm to the side of each chamber, which pulls blood into the chambers. The lower clamps then close, the upper clamps (between pump and dialyzer inlet) open, and positive pressure applied to the diaphragm pushes the blood from the chamber and towards the dialyzer. The chambers fill and empty in unison for SN dialysis and alternate, one filling while the other empties, in DN operation. It is stated that the pump is part of the arterial bloodline and designed as a single-use disposable. Such a disposable may operate with simple blood flow paths, but needs a special dialysis machine containing a pneumatic system for generating alternating positive and negative pressures within the pump chambers. The dialysis machine must also be provided with adequately controlled clamps.
US2010/0241062 discloses a medical fluid pump system comprising reciprocating piston heads which are attached to a membrane that defines a pair of fluid pump chambers. Thereby, the pump system contains a pair of mechanically actuated membrane pumps. The movement of fluid into and out of the fluid pump chambers is controlled by selectively inflating and deflating inflatable members, which thereby are brought into and out of contact with depressible dome regions in flow channels extending to the fluid pump chambers.
The prior art also comprises WO2009/127627, which aims at eliminating the need for pressure sensors in the blood lines of the extracorporeal circuit in a dialysis system. This is achieved by arranging one or more membrane pumps as blood pumps in the extracorporeal circuit, and using the dialysis fluid as working medium of the membrane pump, whereby the pressure of the dialysis fluid may be monitored for measuring the pressure of the blood in the extracorporeal circuit.